1. Field of the Invention
The present invention relates to an ultrasonic surgical instrument used for clotting/incising with respect to a body tissue in, for example, a surgical procedure.
2. Description of the Related Art
When an abdomen of a patient is incised and undergoes a surgical operation or when a surgical operation is conducted by utilizing an endoscope, an ultrasonic surgical instrument is generally used as means for clotting and incising with respect to body tissue. The ultrasonic surgical instrument includes an ultrasonic transducer generating ultrasonic vibration and an ultrasonic probe configuring a surgical section. Ultrasonic vibration generated by the ultrasonic transducer is amplified and transmitted to the ultrasonic probe, where clotting/incising with respect to a body tissue is performed by utilizing the ultrasonic vibration.
As an ultrasonic transducer used in the ultrasonic surgical instrument, an apparatus having a bolt-tightening Langevin type transducer structure (for example, see U.S. Pat. No. 6,068,647 [Patent Document 1]) or an apparatus having a magnetostriction type transducer structure (for example, see U.S. Pat. No. 6,214,017 [Patent Document 2]) are known. The structure of the bolt-tightening Langevin type transducer has such a configuration that piezoelectric elements and electrodes are alternately stacked and the stacked body is arranged between a horn and a backing plate in a fastening manner. The structure of the magnetostriction type transducer has such a configuration that magnetostriction material is wound by a coil.
Recently, as a candidate of material for artificial muscle, it is considered that electrostrictive polymer such as silicon resin or acrylic resin which is polymer material with electric field response called “dielectric elastomer” is used. For example, see Nikkei Science, February 2004 issue, pp. 56-65 (Non-Patent Document 1), Electronic Packaging Techniques 2002.1 (Vol. 18 No. 1) pp. 32-38 (Non-Patent Document 2), and Mold Working: Vol. 16 No. 10 2004 pp. 631-637 (Non-Patent Document 3). The electrostrictive polymer includes electrodes formed on both faces thereof in a thin film manner. When voltage is applied between both the electrodes, such an action that one face side is shrunk and the other face side is stretched occurs. In an actuator using such an electrostrictive polymer, the electrostrictive polymer shrinks and stretches to generate desired driving force according to cyclic application of voltage between the electrodes.
As a usage example of such an actuator utilizing an electrostrictive polymer, application to a prosthesis such as an artificial hand, an artificial leg, a haptic, a soft skin allowing sensing, or a pump for diagnosing blood or the like, or medical equipment has been researched (for example, see Non-Patent Document 3).